1. Field of the Invention
The present invention relates to a matrix for dental medicine which serves as a formwork or shuttering when fillings are inserted into dental cavities and which comprises a band-like blank of a two-layer material, in which one layer is opaque and the other layer transparent, as well as a device for the fabrication of bands of matrices.
2. Description of the Related Art
The objects of the known, differently shaped matrices in the conserving dental medicine are as follows. It is the purpose of the matrices to supply walls lost through caries, due to abrasion and cavity preparation (elimination of caries) during the insertion of the filling into the cavity along the lines of a formwork or shuttering used in construction engineering. By way of a "female mold" it is the purpose of the matrix to restore the lost wall of the tooth --for the most part in Class II cavities--to make the accurate insertion of the filling possible and to secure the marginal termination cervically, i.e. within the area of the neck of the tooth. The subsequent filling then constitutes the "patrix" in a manner of speaking.
In dental medicine, increasing use is made of plastic as material for fillings. The same has to be cured on or in the tooth after having been inserted into the cavity, process which presents certain difficulties since the curing has to take place first within the lower areas in the proximity of the tooth since otherwise, when the free plastic portions located at the top, due to the shrinkage of the cured plastic materially, particularly within the internal contact areas of tooth and plastic, cracks or hollow spaces come into being.
The fundamental problem of the curing of plastic which is effected with the aid of Luminous energy and of supplying the same to the areas of the filling which are located below is solved by means of the so-called illuminating wedges which are capable of conveying or directing the incident light by deflection to the desired and, for the most part, hidden points.
However, what still presents a problem are the so-called matrices which not only have to make the geometrically as correct as possible filling of the cavities possible in the form of a formwork or shuttering, but also the curing of the inserted plastic while being mounted on the tooth.
From the U.S. Pat. No. 4,523,909, a matrix for the dental medicine is known which serves as a formwork when fillings are inserted into dental cavities. This matrix is comprised of a band-shaped blank of a metallic material; it consequently is opaque. This metallic blank on the side which faces the filling, is coated with a plastic film or sheeting which may be transparent or opaque, whereby, however, a transmittivity of light through the matrix is not achieved. The matrix itself does not possess any transparent area or a transparent window. Due to the circumstance that the matrix is comprised of opaque material, no possibility exists of employing plastic that is capable of being cured by light as material for the fillings.